1. Field of the Invention
The present invention relates to a power transmission device incorporated in a filter cigarette manufacturing system and a device for moving cigarettes or filter cigarettes in the axial direction thereof with the aid of the power transmission device during the manufacture of the filter cigarettes.
2. Description of the Related Art
A filter cigarette manufacturing system or a so-called filter attachment includes a first cutting stage, separation stage, feeding stage, connection stage, second cutting stage, and inspection stage. In the first cutting stage, each two cigarettes are obtained by cutting a cigarette rod twice as long as each cigarette into two equal parts. In the separation stage, the two cigarettes are separated from each other so that a predetermined space is secured between them. In the feeding stage, a filter plug is fed into the space between each two cigarettes. In the connection stage, a paper piece is wound around the two cigarettes and the filter plug to connect them, whereby a double filter cigarette is obtained. In the second cutting stage, the double filter cigarette is cut into two equal parts, that is, two filter cigarettes. These filter cigarettes are checked up in the Inspection stage. These stages are executed in the process of continuously transporting the cigarettes or filter cigarettes on grooved drums while rotating the grooved drums.
In the separation stage, each two cigarettes are moved oppositely to each other in the axial direction thereof, so that the predetermined space for receiving the filter plug is formed between these cigarettes.
In the feeding stage, moreover, the two cigarettes must be moved in the axial direction to be brought into intimate contact with the filter plug.
Also in the inspection stage, the two filter cigarettes are moved oppositely to each other in the axial direction thereof, so that a space for receiving an inspection device is secured between these filter cigarettes.
To attain this, devices for axially moving the cigarettes and filter cigarettes are incorporated in the separation, feeding and inspection stages of the filter attachment. An example of these devices is disclosed in U.S. Pat. No. 4,746,006.
The disclosed moving device comprises a pair of first conical drums which are used to receive each two cigarettes obtained in the first cutting stage. These first conical drums are mounted on a first common sleeve so that their respective axes of rotation are inclined oppositely to each other. Thus, each two cigarettes received individually by the paired first conical drums are axially separated from each other as the drums rotate. The moving device further comprises a pair of second conical drums which are used to receive the cigarettes individually from the first conical drums. The second conical drums have the same shape as the first ones. The paired second conical drums have a function to further separate the two received cigarettes, align them on the same axis, and feed them to the next stage.
According to this disclosed moving device, the axes of rotation of the paired conical drums are inclined, so that a pair of bevel gears, whether spiral or straight, are used not only for transmission of power to one conical drum but also for power transmission between the drums.
The paired bevel gears, for use as power transmission means, are mechanical elements which are suited for equal-speed transmission between members whose axial angles are greatly different. Use of these bevel gears, however, is subject to the following drawbacks.
Working the bevel gears of this type, whose specifications are special, is very difficult. Further, the bevel gears must be designed in accordance with the necessary size of the space between each two cigarettes, that is, the length of the filter plug, so that their costs are very high.
Furthermore, the bevel gears require high-accuracy installation. If the backlash of the paired bevel gears is too small, deterioration of the gears is promoted. If the backlash is too great, on the other hand, there is a difference between the rotational phases of the conical drums, so that the cigarettes cannot be securely delivered between the first cutting stage and the paired first conical drums or between the first and second conical drums.
Shims are used for high-accuracy installation of the bevel gears and the conical drums. Before the gears and the drums are determinately installed with the aid of the shims, however, assembling and disassembling these elements should be repeated many times. Thus, the installation of the conical drums and the bevel gears takes much time and labor.
Since bearings for the bevel gears are subjected to thrust load, the gears must be supported by means of thrust bearings. Inevitably, however, deep-groove ball bearings should be used for the purpose in consideration of ease of maintenance, and these bearings undergo early deterioration.
The tooth surfaces of the bevel gears require protection against dust as well as lubrication. To attain this, a bellows-shaped rubber cover is put on the paired bevel gears so as to conceal them externally.
Since the rubber cover repeatedly extends and contracts as the bevel gears rotate, however, it also undergoes early deterioration. In order to avoid being bit by the bevel gears, moreover, the rubber cover is disposed in sliding contact with a receiving member, so that its deterioration is further accelerated.
If the bearings, rubber cover, or other expendables undergo an impermissible degree of deterioration, they must be replaced with new ones. The replacement of these components requires suspension of the operation of the filter attachment, thus lowering the efficiency of production of the filter cigarettes.